This invention relates to an rpm regulator for fuel injection pumps associated with internal combustion engines of the type having an intermediate lever pivotably mounted about a shaft to which a fuel quantity control sleeve is coupled and a centrifugally operated device for generating an rpm signal and applying a corresponding force against the force of a regulator spring assembly to the intermediate lever and thereby to the fuel quantity control sleeve. The present invention relates, more particularly, to such an rpm regulator in which the centrifugally operated device is positioned in the suction chamber of the pump, the chamber being filled with fuel. The device for developing and transmitting an rpm signal includes an axial guide shaft of a centrifugal regulator and the displaceable governor sleeve. The frontal end of the governor sleeve is in contact with the intermediate lever and acts against an arbitrarily alterable force of the regulating spring assembly. Fuel quantity fed by the injection pump is determined by the position of the intermediate lever, the volume of the working chamber being varied with simultaneous fuel delivery through a throttle aperture connecting the working chamber with the suction chamber.
In known rpm regulators of such type the frontsided closed governor sleeve of the centrifugal regulator is displaced by action of centrifugal weights which are mounted about a guide shaft. The governor sleeve has a throttle bore on the frontal end, through which a working chamber, located between the guide shaft and the governor sleeve is connected with the suction chamber. When a volume change in the working chamber occurs because of displacement, the fuel is advanced through the throttle bore and thereby the adjusting motion of the regulator sleeve is damped. Consequently, damping is achieved which is effective over the entire rpm range in this prior art arrangement. Each type of a fuel engine, however, has an rpm or a load range at which it is especially sensitive to detrimental, mechanical, interruptive, nuisance oscillations which influence undesirably the control of the fuel injection quantities. The rpm and load ranges often differ only because of small structural changes in different types of internal combustion engines. According to the type of use to which the particular internal combustion engine is to be put, for example, for the propulsion of a vehicle or of a generator, it may be necessary or desirable to provide for a specific damping characteristic range or ranges, related to a particular load range for the rpm regulator of a fuel injection pump.
The critical range, at which the governor sleeve should not be damped but over which the full, fast-acting speed control of the regulator should be used, is the lowest load range, i.e. the idle range of internal combustion engines, such as those which are specifically designated for the propulsion of motor vehicles. The same is true, in other instances, for the highest load and final rpm range in internal combustion engines which are designated, for example, specifically for driving generators. In an internal combustion engine designated to drive a motor vehicle, it may happen that due to sluggishness of the regulator during a desired fast reduction in rpm, among other things, the internal combustion engine goes into a lower than desired preadjusted rpm range. This so called undercutting or overshooting must be corrected as soon as possible by means of a regulator since otherwise during idling, in an unfavorable case, due to the low drive rpm moment, the internal combustion engine may undesirably come to a standstill. Damping in this range would slow down the regulating velocity and would cause undercutting with detrimental consequences. On the other hand, the top load range of an internal combustion engine used in such a way has a relatively high non-uniformity characteristic, and can be damped substantially without disadvantage. Should the internal combustion engine, for example, be revved to the uppermost rpm range by a sudden acceleration, then the large non-uniformity degree is sufficient, even during damping, to obtain a fast control before overreaching of the maximum desired rpm.
On the other hand, when the internal combustion engine is used for driving a generator, then the fuel injection pump has the lowest possible non-uniformity range for maintaining the given rpm as exact as possible under variable loads of the generator. Here, damping in the upper load range is undesirable for such internal combustion engines, because the regulator must correct the rpm deviation as soon as possible.